1. Field of the Invention
The invention relates to a backlight unit, and more particularly, to a backlight unit capable of improving image quality and a liquid crystal display (LCD) device having the backlight unit.
2. Related Art
Cathode ray tubes (CRT) are widely used for televisions and monitors for measurement devices, information terminals, etc. However, due to the innate weight and size of CRTs, it is difficult to aggressively deal with the miniaturization and weight reduction of electronic devices.
In contrast, LCD devices have the advantages of lightweight, low consumption power, full color, high resolution, and large scale compared with CRTs. Thus, LCD devices are used in a wide range of fields.
Since LCD devices are light-receiving type device that adjust the amount of light supplied from an external source to display an image, LCD devices require a backlight unit to emit light. According to the positions from which light is emitted, backlight units are largely divided into edge-type and top-bottom-type units. A backlight unit may include a light source that emits light. Types of the light source includes an electro luminescence (EL), light emitting diode (LED), cold cathode fluorescent lamp (CCFL), external electrode fluorescent lamp (EEFL), and hot cathode fluorescent lamp (HCFL).
An LED backlight unit that has an almost limitless service life, high brightness, and capability of being miniaturized is being developed. This LED backlight unit is applicable in everything from the smallest display devices to large-scale display devices.
FIG. 4 is a perspective view of an LCD device according to the related art. Referring to FIG. 4, a reflective plate 116 and the light guide plate 115 are held in the molded frame 117, the LED chip 121 is disposed so that its top surface faces the bottom of the holding space 117a at one side of the molded frame 117, and the LED chip 121 is mounted to a flexible PCB 118. The flexible PCB 118 is disposed between a protruded portion 115a and the molded frame 117. That is, a first portion 118a of the flexible PCB 118 is disposed on the molded frame 117, and a second portion 118b of the flexible PCB 118 is disposed over the protruded portion 115a of the light guide plate 115. The protruded portion has a slanted and protruded shape. However, as the flexible PCB 118 is not attached to the light guide plate 115, a gap is generated between the flexible PCB 118 and the protruded portion 115a of the light guide plate 115.
An optical sheet 114 is disposed on the light diffusion plate 115. The optical sheet 114 may include a diffusion sheet 114a and first and second prism sheets 114b and 114c. 
An LCD panel 10 including a color filter substrate 100a and an array substrate 100b may be disposed on the light guide plate 115. An upper polarizing plate 130a and a lower polarizing plate 130b are attached respectively to the top and bottom surfaces of the LCD panel 100.
A backlight unit includes the flexible PCB 118 on which an LED chip 121 is mounted, the light guide plate 115, a reflective plate 116, and the optical sheet 114.
A light-shielding tape 112 maybe interposed between the light guide plate 115 and the LCD panel 110 to block light leaking upward from the edges of the light guide plate 115. However, in a related art LED backlight unit, there is a gap between the PCB and the light guide plate, so that the red, green, and blue light is progressed parallel to the light guide plate through the gap. In this case, since the emitted directions of each light have high brightness compared to other directions, light is radiated in lines. Since light emitted in lines cannot obtain uniform brightness, image quality deteriorates.